Why do only some nuclear lysis buffers create DNA 'goop'

There is a goopy snotty DNA substance that appears after lysing cells in some nuclear lysis buffers (like buffer from ChIP kits), but not with other lysis buffers (like buffers for collecting the nuclear fraction of protein/nuclear extraction). It appears you can lyse nuclei without creating DNA "goop", so what causes it sometimes and not other times? Where does the DNA disappear to when collecting nuclear fractions?